Apparatus for coating a torsional vibration damper weight

ABSTRACT

A fluidized bed coating apparatus is used to substantially cover the weight of a torsional vibration damper with a thin coating of nylon. The apparatus comprises a weight-carrying support rotatably mounted in a tank and a drive motor connected to the support to rotate it during coating of the weight.

United States Patent [191 Bragg et al.

[4 1 Feb. 19,1974

[ APPARATUS FOR COATING A TORSIONAL VIBRATION DAMPER WEIGHT [75] Inventors: Gary 0. Bragg; Russel F. Bahr;

Shellie P. Williamson, all of Peoria, 111.

[73] Assignee: Caterpillar Tractor Co.,- Peoria, 111.

[22] Filed: Aug. 21, 1972 [21] Appl. No.: 282,496

Related US. Application Data [62] Division of Ser. No. 146,257, May 24, 1971, Pat. No.

[52] US. Cl 118/416, 118/503, 269/8 [51] Int. Cl. B05c 3/00 [58] Field of Search 118/DIG. 5, 503, 56,416; 1l7/DIG. 6; 269/8; 279/1 H [56] References Cited UNITED STATES PATENTS 3,278,998 10/1966 Tingquist et al. 118/56 X 3,503,435 3/1970 Dunlop l18/425 X 1,281,762 lO/l9l8 Carpenter..... 1,476,817 12/1923 Hatfield 118/503 Primary ExaminerMorris Kaplan Attorney, Agent, or Firm-Fryer, Tjensvold, Phillips & Lempio ABSTRACT A fluidized bed coating apparatus is used to substantially cover the weight of a torsional vibration damper with a thin coating of nylon. The apparatus comprises a weight-carrying support rotatably mounted in a tank and a drive motor connected to the support to rotate it during coating of the weight.

2 Claims, 6 Drawing Figures MACHINE CLEAN PRIMER HEAT NY LON COAT PAIENTEB FEB I 9 1974 saw 1 a? Q P AIENI FEB 1 9 I974 SHEET 1% 0E .CQOU ZOJ 2 All EMEFE BACKGROUND OF THE INVENTION A torsional vibration damper may be attached to the crankshaft of an internal combustion engine to dampen vibrations occasioned during operation thereof. Such vibrations generate dynamic forces which would normally tend to twist the crankshaft and to subject attendant mechanisms to damage. Conventional dampers, such as the ones disclosed in US. Pat. Nos. 3,234,817 and 3,512,612, both assigned to the assignee of this application, have proven highly successful for damping and tuning purposes. The weights employed in such dampers are normally coated with a bearing material by conventional dipping or spraying techniques or the like.

SUMMARY AND OBJECTS OF THIS INVENTION An object of this invention is to provide a fluidized bed coating apparatus for uniformly and economically coating an object, such as the above-mentioned torsional vibration damper weight, with a layer of bearing material while yet maintaining a high degree of quality control thereover. The apparatus comprises a fixture, including a support means mounting the object thereon, and means for rotating the support means.

DESCRIPTION OF THE DRAWINGS Other objects of this invention will become apparent from the following description and accompanying drawings wherein:

FIG. I is a cross-sectional view of a torsional vibra tion damper, taken in the direction of arrows II in FIG. 2;

FIG. 2 is a partially sectioned, side elevational view of a portion of the damper;

FIG. 3 is an enlarged sectional view of the lower portion of the damper as illustrated in FIG. 1;

FIG. 4 is an exploded isometric view of major components employed in the damper;

FIG. 5 is a schematic flow diagram, including the apparatus of this invention, illustrating steps employed in a method for fabricating an annular weight employed in the damper; and

FIG. 6 is a view taken in the direction of arrows VIVI in FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT The FIGS. l-4 damper is disposed on a central rotational axis X and comprises an integrated hub and housing assembly 10 adapted to be attached to a crankshaft ll of an internal combustion engine by circumferentially spaced bolts 12. The housing assembly com via one of the ports 20 and the ports are thereafter closed by means of a lead seal 21 and overlying expansion plug 22 mounted in a counterbore 23. The second port is utilized for air purging purposes during the filling operation.

An annular inertia weight 24 is rotatably mounted in a closed chamber, defined by the opposed sidewalls and inner and outer walls of the housing, to cooperate with the surrounding silicone fluid to provide the damping and tuning desiderata. The weight is rotatably mounted on an axially disposed hub or inner wall 25 attached to a radially disposed flange 26 attached to crankshaft 11. The weight may comprise an iron casting or other weighty material substantially covered with a plastic bearing material or coating 27, such as nylon, Teflon or bronze having uniform thickness approximating 0.015 in., secured on a conventional primer 28, such as a 253-1 primer manufactured by the M & T Chemical Co., as will be hereinafter more fully described. In addition to the bearing contact provided the plastic material prevents contact between the metallic weight and housing and further prevents corrosion of the weight.

A plurality of radial passages 29' are formed through the weight and coating 27 to communicate the viscous fluid from chamber portions 30 to clearances 31, defined between the weight and the sidewalls and outer wall of the housing. The clearances are precisely defined and maintained during damper operation by means of axially aligned annular shoulders or spacing means 32 and 33, formed at the radially inner portion of the weight. Chamber portions 30, similar to those described in US Pat. No. 3,512,612, normally retain a substantially large portion of the silicone fluid and are pre-fabricated in the form of recesses defined by circumferentially spaced and raised surface portions 34 formed on hub 25 of the housing.

Referring to FIGS. 5 and 6, inertia weight 24 is first suitably cast and machined, including the drilling of radial passages 29. One of the passages is preferably tapped at the radially outer end thereof, as shown at 35 in FIG. 1, to provide threads adapted to have an eye bolt secured therein for transport purposes. The exposed surfaces of the weight are then cleaned by subjecting them to grit blasting or the like.

The weight is then coated with a standard primer 28, preferably approximating 0.002 in. :in thickness, by dipping it into a primer containing tank, for example. The weight is then placed in an oven wherein it is heated to a temperature preferably in the range of from 450F. to 550F. The heated weight is removed from the oven and mounted on a fixture 36 for application of nylon coating 27 thereon. The fixture is selectively lowered into a tank 37 of a fluidized bed coating apparatus of the type disclosed in US. Pat. No. 2,974,059.

In general, the fluidized bed coating process comprises the steps of discharging a pressurized gas, such as air or nitrogen, through a control valve 38 and into a lower chamber 39. The gas passes upwardly through a porous ceramic plate means 40 and into an upper chamber 41 to suspend powdered nylon particles 42 therein. The powdered nylon is uniformly suspended in a continuously fluidized bed which contacts the heated surface portions of weight 26 to coat same. It should be noted that the pores formed through plate 40 are suitably sized to permit the air to move upwardly, but to prevent the nylon powder from descending therethrough.

Fixture 36 comprises a support 43 adapted to be moved vertically by a conventional hoist mechanism 44. A bull gear 45 is rotatably mounted on the support to engage with a pinion gear 46 adapted to be selectively driven by an air motor 47. A support means 48 is secured to the bull gear and has three circumferentially spaced brackets or mounting means 49, 50 and 51 attached thereto. The brackets may be magnetized to further assure precise and positive mounting of the weight on the fixture.

Lowerbrackets 49 and 50 are fixedly secured to the support whereas bracket 51 is hingedly connected at 52 thereon for selectively mounting the weight on the fixture. The latter bracket has tapered pin 53 secured thereto for engaging the upper passage 29 for centering and securance purposes. In FIG. 6, bracket 51 is further shown in a dotted line or raised position which facilitates removal of the inertia weight from the fixture when it is raised out of chamber 41 by means of hoist mechanism 44. As shown in FIG. 4, portions of the brackets function as masks" to prevent adherence of the nylon coating to portions 54 of the weight to provide gauge means for subsequent machining operations.

In particular, the dimensional tolerances of the weight must be held very close for correct installation in the dampers housing. Since the nylon coating will initially exhibit a somewhat non-uniform thickness, cutout portions 54 may be used for precise, three-point chucking purposes to achieve close machining tolerances. Dimensional integrity, including a substantially even thickness of the nylon coating on the weight, are thus assured.

Upon removal of the coated weight from fixture 38 and subsequent machining thereof, the weight is centered on raised portions 34 of the housing and O-ring seal 17 is seated in groove 18 (FIGS. 1 and 3). Plate 14 is then secured to case 13 by electron-beam welds l and 16. The plate preferably has conically shaped, annular grooves 55 and 56 formed thereon to assure the desired penetration of welds and 16 through the plate and into the case. In addition, the welds will not protrude beyond the outer surface of the plate which might inhibit correct assembly of a drive pulley or the like thereon. Also, the welding operator is provided with an accurate line or template on which to weld.

Chamber 19, including chamber portions 30, is

thereafter filled with a viscous fluid via one of the ports 20. The second port permits air to escape during the filling operation wherein the damper is maintained horizontally. When the chamber has received the proper amount of fluid, lead seals 21 are placed within counterbores 23 of ports 20 (FIG. 3) and locked in place by means of expansion plugs 22.

What is claimed is:

1. A fluidized bed coating apparatus for coating an object with a layer of material comprising a tank having a porous plate means secured therein to define separated upper and lower chambers,

means for communicating a gas to said lower chamher,

a fixture normally positioned in said upper chamber, including support means and mounting means for mounting an object on said support means,

means for rotating said support means,

said mounting means comprising a plurality of brackets attached to said support means and circumferentially spaced thereon, at least one of said brackets being pivotally mounted on said support means,

means for selectively raising said fixture out of said tank,

said means for rotating said support means comprising a motor mounted on said fixture and gear means operatively connected between said motor and said support means for rotating said support means upon actuation of said motor,

said gear means comprising a pinion gear driven by said motor and a bull gear meshing with said pinion gear and secured to said support means, and

three of said brackets being disposed on said support meant.

2. The invention of claim 1 wherein each of said brackets is magnetized. 

1. A fluidized bed coating apparatus for coating an object with a layer of material comprising a tank having a porous plate means secured therein to define separated upper and lower chambers, means for communicating a gas to said lower chamber, a fixture normally positioned in said upper chamber, including support means and mounting means for mounting an object on said support means, means for rotating said support means, said mounting means comprising a plurality of brackets attached to said support means and circumferentially spaced thereon, at least one of said brackets being pivotally mounted on said support means, means for selectively raising said fixture out of said tank, said means for rotating said support means comprising a motor mounted on said fixture and gear means operatively connected between said motor and said support means for rotating said support means upon actuation of said motor, said gear means comprising a pinion gear driven by said motor and a bull gear meshing with said pinion gear and secured to said support means, and three of said brackets being disposed on said support meant.
 2. The invention of claim 1 wherein each of said brackets is magnetized. 